SPOJ QTREE Query on a tree （树链剖分）

树链剖分裸题。。

#include<iostream>#include<string>#include<cstring>#include<cstdio>#include<cmath>#include<queue>#include<set>#include<algorithm>using namespace std;#define LL long long#define eps 1e-8#define MP make_pair#define N 200020#define M 400020#define NLGN 400002#pragma comment(linker, "/STACK:1024000000,1024000000")#define ls (i << 1)#define rs (ls | 1)#define md ((ll + rr) >> 1)#define lson ll, md, ls#define rson md + 1, rr, rs#define mod 258280327#define inf 0x3f3f3f3f#define pii pair<int, int>#define ULL unsigned long longint readint() {    char c;    while((c = getchar()) && !(c >= '0' && c <= '9') && c != '-');    int ret = c - '0', sgn = 0;    if(c == '-') sgn = 1, ret = 0;    while((c = getchar()) && c >= '0' && c <= '9')        ret = ret * 10 + c - '0';    if(sgn) ret = -ret;    return ret;}char buf[8000000],*pt = buf,*o = buf;int getint(){    int f = 1,x = 0;    while((*pt != '-') && (*pt < '0' || *pt > '9'))    pt ++;    if(*pt == '-')    f = -1,pt ++;    else    x = *pt++ - 48;    while(*pt >= '0' && *pt <= '9')    x = x * 10 + *pt ++ - 48;    return x * f;}char getch(){    char ch;    while(*pt < 'A' || *pt > 'Z')    pt ++;    ch=*pt;pt++;    return ch;}int n;int fst[N], nxt[M], vv[M], cost[M], e;int buttom[N];int dep[N], sz[N], son[N], fa[N], val[N];int tid[N], lab[N], tp[N], dc;int mx[N<<2];void init() {    memset(fst, -1, sizeof fst);    e = 0;}void add(int u, int v, int c) {    vv[e] = v, cost[e] = c, nxt[e] = fst[u], fst[u] = e++;}void dfs(int u, int p, int d) {    fa[u] = p, sz[u] = 1;    dep[u] = d, son[u] = 0;    int mx = 0;    for(int i = fst[u]; ~i; i = nxt[i]) {        int v = vv[i];        if(v == p) continue;        buttom[i/2+1] = v;        val[v] = cost[i];        dfs(v, u, d + 1);        sz[u] += sz[v];        if(mx < sz[v]) mx = sz[v], son[u] = v;    }}void dfs1(int u, int anc) {    tid[u] = ++dc;    lab[dc] = u;    tp[u] = anc;    if(son[u]) dfs1(son[u], anc);    for(int i = fst[u]; ~i; i = nxt[i]) {        int v = vv[i];        if(v == fa[u] || son[u] == v) continue;        dfs1(v, v);    }}void build(int ll, int rr, int i) {    if(ll == rr) {        mx[i] = val[lab[ll]];        return;    }    build(lson);    build(rson);    mx[i] = max(mx[ls], mx[rs]);}int query(int l, int r, int ll, int rr, int i) {    if(ll == l && rr == r) return mx[i];    if(r <= md) return query(l, r, lson);    if(l > md) return query(l, r, rson);    return max(query(l, md, lson), query(md + 1, r, rson));}void update(int x, int v, int ll, int rr, int i) {    if(ll == rr) {        mx[i] = v;        return;    }    if(x <= md) update(x, v, lson);    else update(x, v, rson);    mx[i] = max(mx[ls], mx[rs]);}int f(int u, int v) {    int ret = -inf;    while(tp[u] != tp[v]) {        if(dep[tp[u]] > dep[tp[v]]) swap(u, v);        ret = max(ret, query(tid[tp[v]], tid[v], 1, n, 1));        v = fa[tp[v]];    }    if(dep[u] > dep[v]) swap(u, v);    if(u != v)        ret = max(ret, query(tid[u] + 1, tid[v], 1, n, 1));    return ret;}int main() {    int cas;    scanf("%d", &cas);    while(cas--) {        scanf("%d", &n);        init();        for(int i = 1; i < n; ++i) {            int u, v, c;            scanf("%d%d%d", &u, &v, &c);            add(u, v, c);            add(v, u, c);        }        dfs(1, -1, 0);        dc = 0;        dfs1(1, 1);        build(1, n, 1);        char op[10];        while(scanf("%s", op) && op[0] != 'D') {            int x, y;            scanf("%d%d", &x, &y);            if(op[0] == 'Q') {                printf("%d\n", f(x, y));            }            else {                update(tid[buttom[x]], y, 1, n, 1);            }        }    }    return 0;}